The present invention relates to a synthetic fiber rope, preferably of aromatic polyamide material.
Especially in materials handling technology, for example on elevators, in crane construction, and in open-pit mining, etc., ropes are an important element of machinery and subject to heavy use. An especially complex aspect is the loading of driven or over pulleys deflected ropes, for example as they are used in elevator construction.
Specifically, on elevator installations the lengths of rope needed are large, and considerations of energy lead to the demand for smallest possible masses. High-tensile synthetic fiber ropes, for example of aromatic polyamides or aramides with highly oriented molecule chains, fulfil these requirements better than conventional steel ropes.
Specifically, ropes constructed of aramide fibers have a substantially higher lifting capacity than conventional steel ropes of the same cross section, and only between one fifth and one sixth of the specific gravity. However, the atomic structure of aramide fiber causes it to have a low ultimate elongation and a low shear strength.
Such an aramide fiber rope with parallel lay is known, for example, from European patent document EP 0 672 781 Al. There, between the outermost and inner layers of strands there is an intersheath which prevents contact between the strands of different layers and thereby reduces the wear due to their rubbing against each other. The aramide rope described so far has satisfactory values of service life, resistance to abrasion, and fatigue strength under reversed bending stresses. However, when loaded under tension the twisted stranded synthetic fiber rope has a tendency to rotate about its longitudinal axis and/or untwine. The undesirable untwining of the stranded rope can lead to an unevenly distributed loading of the strands of different strand length over the cross section of the rope and thereby to a reduction in the breaking load of the rope or even to failure of the rope.